San Francisco Frontiers - 'Malfunction' cuts power in Ukraine. Here's what we know

The outages knocked out water supplies to Ukraine's capital, Kyiv, and prompted a rare shutdown of the city's metro network, paralysing transport for thousands of residents.

Authorities restored power to most critical infrastructure in Kyiv by around 1200 GMT, Ukraine's energy minister said, but he warned Ukrainian households may have to wait longer for it to return.

Moldova's energy minister said the power would return in his country in "an hour or two".

The issue adds further pressure to Ukraine's already fragile energy grid, which has suffered weeks of intense Russian bombardment.

Here's what we know:

- What happened? -

Officials suggested the power cut was accidental.

The issue began at around 10:42 am (0842 GMT), when a 400-kilovolt line between the power grids of Romania and Moldova and a 750-kilovolt line between western and central Ukraine shut down, Ukraine's energy minister Denys Shmygal said on Telegram.

Ukrainian authorities did not say what caused the lines to fail.

But they have ruled out Russian cyberwarfare.

"As the President (Volodymyr Zelensky) announced, the accident occurred due to technical reasons on the lines between the power grids of Ukraine and Moldova," Ukraine's ministry of digital transformation said.

The Kremlin, which has bombarded Ukraine's energy grid for weeks, said on Friday it was refraining from attacks on Kyiv until Sunday following an appeal from US President Donald Trump.

- Effect on residents -

The shutdown immediately knocked out power in Kyiv and the surrounding area, as well as in the Zhytomyr and Kharkiv regions.

The outage disrupted water supply in "all city districts of Kyiv", according to municipal utility firm Kyivvodokanal.

The Kyiv metro shut down all its lines, a rare occurrence in its 65-year history.

Around 800,000 passengers use the system daily, according to data published last year. Many of them rely on it to commute to work.

Residents also use its 52 stations as bomb shelters during Russian attacks.

A major part of Moldova's capital, Chisinau, was left without electricity, Mayor Ion Ceban said.

Traffic lights also stopped working, prompting police to deploy to intersections.

The power cuts also affected the operation of Ukraine's three operational nuclear plants, which had to "unload" their capacity following the outage, the energy ministry said.

"Gradually loading nuclear power plant units to their nominal capacity takes time," it added.

The site of Ukraine's defunct Chernobyl nuclear plant briefly lost off-site power in the shutdown, the UN atomic energy watchdog said.

"No direct impact on nuclear safety expected, but overall situation remains precarious," it added.

- Restoring power -

Zelensky called the outage an "emergency".

Ukraine's largest private energy firm DTEK said it had already restored electricity to critical infrastructure in Kyiv around three hours after the outage.

"Restoration is proceeding in stages. This approach is required to avoid overloading the networks and to prevent new accidents," it added.

But Ukraine's state-owned grid operator expressed caution, saying shortages remained "very high".

"Emergency power cuts are currently in effect in Kyiv city, Kyiv region, Cherkasy region, Chernivtsi region, Zhytomyr region, and Kharkiv region," it said at 1146 GMT.

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L.Nguyen--SFF